This study retrospectively examined the records of patients with clinical N2 (cN2) stage non-small cell lung cancer (NSCLC) who were surgically treated but who actually had pathologic N0 (pN0) stage disease. From 1982 to 1997, 94 patients with cN2 NSCLC underwent surgery. Forty-five patients proved to have pN0 disease, with an overall 5-year survival rate of 67.3%. According to the Cox model, visceral pleural invasion (p=0.01) and a carcinoembryonic antigen (CEA) concentration > or =2.5 ng/mL (p=0.03) negatively influenced survival. The six patients with both visceral pleural involvement and a CEA > or =2.5 ng/mL all died within five years compared with a 78.1% 5-year survival for the 21 patients who had neither factor. For the subgroup of patients who have poor prognostic factors, multimodality therapy should be considered. Our previous report found that parietal pleural invasion, elevated CEA concentration, and the number of involved mediastinal lymph node (MLN) stations correlated with survival in 40 patients with cN2-pN2 disease who underwent resection. These data show how important it is to assess pleural status carefully and measure the CEA concentration, as is to determine the MLN status in patients with cN2 disease.